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[ScreenOS] Unable to manage device via SSL (HTTPS to the device) when using Firefox browser version 32 and later



Article ID: KB30330 KB Last Updated: 27 Dec 2017Version: 2.0

Users are unable to access a ScreenOS device via HTTPS while using Firefox Browser Version 32. This is not an issue with Internet Explorer.


User is trying to access a ScreenOS device via HTTPS which has default self-signed certificate configured. When accessing this, you will get a Firefox Browser page, displaying the message, "This connection is Untrusted". Normally, you would click I Understand the Risk:


and then click Add Exceptions.

Usually, after clicking Add Exceptions, it should proceed normally to the desired page. However, with Firefox version 32, it doesn't do anything & it just stays there.


Beginning with version 32, Firefox no longer accepts certificates with 1024-bit RSA keys. 

​This has been deemed insecure, and the resolution is to re-configure the ScreenOS device to include a 2048-bit RSA key for the self-signed certificate. 

If you have other devices that use 1024-bit RSA keys for default self-signed certificates, you will have to do the same procedure for those devices as well.


The resolution is to configure a local certificate signed with a 2048-bit RSA key (the default is to use a 1024-bit RSA key). 
This requires creating a new key-pair using a 2048-bit RSA key. 

​Please refer to KB16739 - How to manually generate a new system self-signed certificate to replace the expired system self-signed certificate without resetting the firewall for details on configuring a new key-pair, local certificate, and self-signed certificate using a 2048-bit RSA key. In Step 2, use the command exec pki rsa new-key 2048 instead of exec pki rsa new-key 1024 to generate a 2048-bit long key-pair.

Even after configuring this, you may still run into issues accepting the new certificate.  If you do, you may have to clear out the exception lists, by deleting the cert_override.txt and cert8.db file from your Firefox profile folder.  For instructions on navigating to your profile folder, please see

Modification History:
2017-12-27: Article reviewed for accuracy. Minor grammatical change done. Article is correct and complete.

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